The present invention is relates to a fuel injector.
During operation of an engine, a problem generally occurs in the case of direct injection of a fuel into the combustion chamber of an internal combustion engine, particularly in the case of direct gasoline injection or the injection of diesel fuel, that the downstream tip of the injection valve projecting into the combustion chamber is coked by fuel deposits or that soot particles formed in the flame front are deposited on the valve tip. Therefore, in the conventional arrangement of injection valves projecting into the combustion chamber, there is the danger during its lifetime of a negative influence on the spray parameter (e.g., static flow quantity, spray angle, drop size, skeining) that can lead to operational disturbances of the internal combustion engine or to a malfunction of the injection valve.
The injector valve according to the present invention may provide the advantage that the negative effects of coking (soot depositing), e.g., on the valve tip projecting into the combustion chamber including its outlet openings may be restricted or eliminated. Forming a rough surface structure for accumulating combustion-chamber gas with access to the dead volume arranged between valve needle end and the spray region including the outlet openings in accordance with the present invention makes it possible to largely prevent coke deposits in the outlet openings. As a result of the buoyancy of the gas phase with respect to the fluid phase and of the large surface tension, the gas remains in the pores of the rough surface structure for accumulating combustion-chamber gas.
In this manner, the spray parameter and the valve function are able to be maintained in a stable manner during its entire lifetime even in the case of direct injection of fuel into a combustion chamber at the fuel injection valves.
A rough, porous surface structure may be provided on the valve needle end facing the outlet openings, i.e., on the surface of the valve-closure member facing the dead volume. The surface structure may be produced via roughening (cavity sinking, flash-etching, grinding with a coarse grain, introducing turning scores or grooves or the like) or by sintering the appropriate component part.
In addition, the pores of the rough surface that accumulate gas may also be used as vapor-forming nuclei, so that when the vapor pressure is not sufficient vapor bubbles of fuel are formed in the pores.